WHAT IS PORTLAND CEMENT?

New Zealand Herald, Volume XVIII, Issue 6149, 2 August 1881, Page 6

WHAT IS PORTLAND CEMENT?

' .. ' ' TO THE EDITOR. Sib,—ln your issue of July 11th, Mr. N. Wilson states that my cement ie as far from being Portland cement as the poles are asunder. For the purpose of: enlightening that gentleman, as to the character of the cement manufactured by myself, and for the guidance of such of the public as may have •been niisled'by'his letter to you on the eubject, I have to askyou to publish the following information :—There are two testa, and two only, .which determine'the nature and quality of a building cement. The first is chemical analysis; the second is that of the engineer. Portland cement gives well-known results in both cases, and no other cement can give the same. Of this fact Mr. Wilson

appears to be wholly ignorant. Neither the process of manufacture nor the employment of several materials in such manufacture has, as I have had occasion to say before, the remotest connection with or affords the least reason for or against the name Portland cement. A cement is properly so called when it has certain chemical constituents, and behaves in a certain way under the engineer's test. I sha.ll now show that my cement is true Portland, and nothing else according to these criteria. Its chemical constituents are as follows, according to an analysis reported to me by Dr. Hector: —Lime, 63"37; alumina, iron, oxides, and silica, 25'97 per cent. To this Dr. Hector appends a note :—" This is very finely ground, and, as is'to" be seen by the foregoing statement, has the constitution of a good Portland uement." A high English authority gives the following as th» normal constitution of Portland cement:—

Lime. Silica, Alumina, &c. English, 02 per cent. 35 per cent. German, 6S per cent. 31 per cent.

So that, chemically, my. cement is really identical with the article made in England and Germany. The second test, to which I have referred, comprises three points of detail:—!, Fineness; 2, weight; 3, tensile strain. The New Zealand Government has, as Mr. "Wilson probably knows, a certain definite standard which all cement supplied must attain. The cement must, after passing through a 50 gauge sieve; leave a residue of not more .than 10 per cent,; it must weigh llOlbs. per bushel; and lastly, must stand a minimum tensile strain of 2001bs. to the square inch. The.tests of my manufacture are not yet complete, but from a large number of experiments made officially by the Government District Engineer h.>re I am enabled to say that its tensile strain out of a dozen briquettes averaged 2501b5. .to the square inch. Its weight, as taken by me, is llolbs. per bushel, and the residue after passing, through a 50-&auge sieve is reported to me at 75 per cent. H. Reid, one of the priucipal English authorities on the subject, says, with reference to the standard adopted by the New Zealand Government, which ie that of the London Metropolitan Board of Works at home, that "no cement but a true Portland can pass it." In the face of this statement, of the report of Dr. Hector, and the details above given Mr. Wilson's opinionas to whethor my cement is or is not " Portland" clearly has a value —which is something less than nothing.—Yours, &c, D. Atkinson.